This invention relates to a drive train for a vehicle, and more particularly, to a drive train for restarting and recoupling an internal combustion engine in a vehicle with an automatic transmission wherein the internal combustion engine is selectively disengaged and turned off while the vehicle is coasting.
In German Patent Application No. P 29 45 304.1, there is disclosed an apparatus for actuating a servo control motor to operate a clutch disposed between the driving engine of a vehicle and the wheels when the accelerator pedal is released and the vehicle is coasting. The engine is disconnected and turned off by either cutting off the ignition current or the fuel supply only when the vehicle is coasting faster than a preset speed. When the accelerator pedal is depressed again, the engine is recoupled with the transmission whereby the momentum of the vehicle turns the engine and starts it.
In the disclosure of German Patent Application No. P 29 45 304.1, an automatic transmission for driving the vehicle has two hydraulic pumps. The first pump, a conventional hydraulic pump in an automatic transmission, is driven by the transmission input shaft. When the driving engine is stopped, however, the transmission input shaft does not turn. The hydraulic pump does not operate, and the hydraulically operated clutch cannot be engaged to recouple the engine. A secondary hydraulic pump driven by the transmission output shaft was provided to overcome this difficulty. The secondary pump operates when the vehicle is moving since it is coupled to the wheels through the transmission output shaft. It is evident that the provision of two hydraulic pumps increases the cost and complexity of an automatic transmision, however.
Accordingly, a purpose of the present invention is to provide, in a vehicle in which the driving engine is disconnected and turned off when the vehicle is coasting, a drive train for restarting and recoupling the engine that utilizes a single hydraulic pump.